1. Field of Invention
This invention relates to methods and compositions for preventing and treating disease in poultry.
2. Description of Related Arts
Poultry are domesticated birds that are raised by farmers for meat and eggs. Poultry includes, without limitation, chickens, ducks, geese, turkeys, guinea fowl, and pheasants. An example of a commercially raised duck is the White Pekin duck.
Examples of commercially raised geese are Embden, Toulouse, Chinese goose, African goose, Sebastopol, Pilgrim, and American Buff breeds. Examples of commercially raised turkeys include White, Hollands, Bronze, Narragansett, Bourbon Red, Black, Slate, Royal Palm, Beltsville, and Small White breeds.
Examples of commercially raised chickens include the American Class, the Asiatic Class, the English Class, and the Mediterranean Class. The American Class includes Buckeye, Chantecler, Del., Doninique, Holland, Java, Jersey Giant, Lamona, N.H., Plymouth Rock, R.I. Red, R.I. White, and Wyandotte breeds. The Asiatic Class includes the Brahma, Cochin, and Langshan breeds. The English Class includes the Australorp, Cornish, Dorking, Orpington, Redcap, and Sussex breeds. The Mediterranean Class includes the Ancona, Blue Andalusian, Catalanas, Leghorn, Minorca, Spanish, and Buttercup breeds. As would be appreciated by those of skill in the art, there are classes and breeds of poultry other than those listed above. The invention described herein is generally used on all classes and breeds of poultry.
Avian influenza viruses are diseases that pose significant threats to animal and human health and are a source of genetic diversity that permits the emergence of pandemic influenza. As used herein, avian influenza is influenza that adversely affects at least some poultry by causing flu symptoms, and possibly death, in the poultry. The fact that an influenza can be carried by some poultry without producing flu symptoms or adversely affecting the health of the poultry does not alter the fact that the influenza is an avian influenza and is a disease as long as the influenza adversely affects the health of at least some poultry. As used herein, a poultry that contracts avian influenza virus and that does not exhibit symptoms and/or that functions as a carrier of the virus is still said to have contracted the avian influenza disease. A poultry contracts avian influenza virus when the virus is in the body of the poultry.
As used herein, a disease is prevented before or after poultry is exposed to the disease, if (1) a medicament composition is administered to an animal internally (by ingestion, inhalation, injection, etc.), topically (on the skin for absorption into the body), or otherwise, and (2) the medicament composition prevents the poultry from contracting the disease and experiencing symptoms normally associated with the disease, or, if the poultry contracts the disease and experiences or doesn't experience in varying degrees of severity some or all of the symptoms normally associated with the disease, the poultry recovers from the disease to a normal healthy state.
As used herein, a disease is treated if a medicament composition is administered to poultry after the poultry has contracted a disease. As noted above, a poultry that contracts a disease may or may not exhibit symptoms associated with the disease.
The symptoms produced in poultry by avian influenza range from a mild illness to a highly contagious and rapidly fatal “highly pathogenic” form of the disease that can produce severe epidemics. Highly pathogenic avian influenza is characterized by sudden onset, severe and rapid death, and a mortality that can approach 100%.
Fifteen subtypes of influenza virus are known. All outbreaks of the highly pathogenic form that have occurred to date were caused by influenza A viruses of subtypes H5 and H7.
One problem with avian influenza viruses is that viruses of low pathogenicity can, after circulating for a relatively short period of time, mutate in highly pathogenic viruses.
Another problem with avian influenza viruses is that they are highly contagious.
A further problem with avian influenza viruses is that they are readily transmitted from farm to farm by mechanical means including, for example, contaminated equipment, vehicles, feed, cages, and clothing.
Still another problem with avian influenza is that highly pathogenic viruses can survive for long periods in the environment, especially when temperatures are low.
Still a further problem with avian influenza is that influenza A viruses, including subtypes from different species (i.e., humans and poultry), can swap or “reassort” genetic materials and merge. This reassortment process is known as antigenic “shift”. Antigenic shift produce a novel subtype different from both parent viruses. Antigenic shift typically results in highly lethal pandemics. Since pigs are susceptible to infection with avian and mammalian viruses, including human strains, pigs can function as a “mixing vessel” for the scrambling of genetic material from human and avian viruses, resulting in the mergence of a novel subtype. Consequently, humans living in close proximity to domestic poultry and pigs have been thought to produce conditions favorable from the emergence of antigenic shift. Recent evidence, however, also suggests that humans themselves can serve as the “mixing vessel”.
There are various routes of transmission of avian influenza. Consequently, a chicken at a first farm can possibly pass avian influenza virus to a pig or farmer at a farm. The farmer can contaminate his clothes and his tractor with the virus. The pig can pass the virus to the farmer, possibly after the pig has served as the “mixing vessel” described above. The avian influenza virus can then be transmitted to a chicken at a second farm via the clothes of the farmer (if the farmer visits farm), via pig (if the pig is sold to farm), and via tractor (if tractor is parked at farm or is used by a farmer inhabiting farm).
Direct avian-to-human influenza transmission was unknown before 1997 when the H5N1 virus jumped from chickens to humans in Hong Kong. Eighteen people were hospitalized, six died and three million chickens were slaughtered to contain the virus.
In 2003, highly pathogenic strains of avian influenza virus, including the H5N1 and H7N7 subtypes, again crossed from birds to humans and caused fatal disease. The year 2004 saw the largest outbreak of H5N1 avian flu in history prompting world governments and health authorities to call for emergency preparedness measures. This outbreak was an economic disaster for the poultry industry, caused loss of human life, and sounded alarm bells of an impending human influenza pandemic. With a human mortality rate of greater than 75%, it has been estimated that a human pandemic involving H5N1 could result in 100 million human deaths worldwide.
A critical step in avoiding a human influenza pandemic involving avian influenza is to reduce the incidence of human exposure to the virus. This can in large part be accomplished by controlling the infections in poultry. However, attempts at poultry vaccination programs for avian influenza have not been successful and there are currently no anti-avian influenza medications available for use by the poultry industry. Accordingly, it would be highly desirable to provide a method and composition for preventing and treating avian influenza in poultry.